Unbelievable claims for fuel economy or MPG for RVs, including the Monaco Vesta, are being tossed around by dealers, blogs, online videos, and a host of other sources. Products claiming wild results on How to Get Better Fuel Economy or MPG in your Motorhome. We've tracked our fuel economy in the Vesta for the past year and there is more to it than just seeing what your on-board computer has to say. RV Manufacturers love to toss around MPG numbers but these numbers aren't backed by ANY research or track testing, so the only way to get accurate information is to track the MPG yourself.